The present invention relates to a method and apparatus for monitoring cigarettes and/or other rod-shaped articles of the tobacco processing industry, and more particularly to improvements in methods and apparatus for scanning the exterior of such rod-shaped articles. Still more particularly, the invention relates to improvements in a method and apparatus for optically or similarly scanning the exterior of cigarettes or similar rod-shaped articles for the presence or absence of certain types of defects which can be detected by resorting to light or other forms of radiation.
The exterior of cigarettes, filter rod sections and/or analogous rod-shaped articles of the tobacco processing industry is likely to exhibit a number of defects, such as open seams, holes, enlarged portions, improperly applied or improperly oriented filter mouthpieces, absence of filter mouthpieces, bends in the tobacco-containing or filter-containing portions of filter cigarettes, cigars or cigarillos, absence of roundness, frayed or open tobacco-containing end portions of cigarettes, cigars or cigarillos, improperly applied uniting bands of tipping paper which is used to affix filter mouthpieces to plain cigarettes, cigars or cigarillos and/or a combination of two or more of the above-enumerated defects.
It is already known to monitor the exterior of a rod-shaped article of the tobacco processing industry with light or other types of radiation. Changes in the characteristics of radiation which are indicative or suggestive of the presence of one or more defects are detected by resorting to a suitable transducer, and the signals which are furnished by the transducer are used to segregate defective articles from satisfactory articles and/or to effect changes which are intended to prevent persistence and/or future development of similar defects in a cigarette rod making, filter tipping, filter rod making or like machine. For example, U.S. Pat. No. 4,011,950 to McLoughlin et al. discloses a cigarette monitoring apparatus wherein light rays are caused to pass along a portion of the periphery of the tested cigarette, namely along the filter plug or filter mouthpiece of a filter cigarette, in order to ascertain whether or not the filter mouthpiece is properly oriented with reference to the tobacco-containing portion of such product. The patented apparatus is further supposed to detect improperly convoluted and/or outwardly extending portions of uniting bands of tipping paper. A drawback of the patented apparatus is that the light source and/or the photoelectric sensor can only be placed close to but not all the way into contact with the periphery of the tested article. This means that such apparatus cannot detect defects which can be detected only if the radiation is caused to propagate itself in immediate proximity of the exterior of the article. For example, a partially projecting portion of a uniting band will not be detected if it does not extend outwardly well beyond the major part of the tested article. This reduces the versatility and particularly the reliability of such monitoring apparatus.
U.S. Pat. No. 4,277,678 to Wahle et al. discloses a modified method and apparatus for testing cigarettes or the like. The article to be tested is set in motion to rotate about its own axis and to thereby move its periphery along a beam of radiation which is caused to propagate itself in parallelism with the axis of the rotating article. The radiation source emits a single light beam which is caused to pass along the entire article and thereupon impinges upon a photoelectric transducer. This method and the apparatus for its practice are quite reliable; however, they can be put to use only under circumstances when the articles to be tested are or can or should be caused to rotate about their own axes.